Browsing by Author "Jeng, SL"

Now showing 1 - 6 of 6

A constrained multibody system dynamics avoiding kinematic singularities
(2002-03-01)
Huang, CF
;
Yan, CD
;
Jeng, SL
;
Cheing, WH
;
機械工程學系
In the analysis of constrained multibody systems, the constraint reaction forces are normally expressed in terms of the constraint equations and a vector of Lagrange multipliers. Because it fails to incorporate conservation of momentum, the Lagrange multiplier method is deficient when the constraint Jacobian matrix is singular. This paper presents an improved dynamic formulation for the constrained multibody system. In our formulation, the kinematic constraints are still formulated in terms of the joint constraint reaction forces and moments; however, the formulations are based on a second-order Taylor expansion so as to incorporate the rigid body velocities. Conservation of momentum is included explicitly in this method; hence the problems caused by kinematic singularities can be avoided. In addition, the dynamic formulation is general and applicable to most dynamic analyses. Finally the 3-leg Stewart platform is used for the example of analysis.
A novel master switching method for electronic cam control with special reference to multi-axis coordinated trajectory following
(2006-02-01)
Chang, YH
;
Chieng, WH
;
Liao, CS
;
Jeng, SL
;
機械工程學系
Multi-axis coordinated trajectory following is important in CNC machines and metal cutting tools. Recently, flight simulators with electrical actuators have been in increasing demand. However, the coordinate control scheme affects the accuracy of the motion because motors have an insufficient load-capacity relative to the hydraulic actuators. The electronic cam (ECAM) is typically used to perform coordinated control. However, selection of the master may determine potentially very different characteristics of motion. This study proposes an automatic master switching method. The conditions and results of the master switching method for ECAM are detailed. The robustness and stability of the proposed control system is also demonstrated using the well-known structured perturbation analysis tool, mu. (c) 2005 Elsevier Ltd. All rights reserved.
Analysis of two-dimensional fixture clamping with friction
(1999-06-01)
Tzen, JJ
;
Jeng, SL
;
Cheing, WH
;
機械工程學系
;
Department of Mechanical Engineering
Fixtures that constrain the unwanted motion of a workpiece are important tools in automated manufacturing today. In this paper, we analyze the stability of clamping with passive friction force. The concept of the instant center of rotation is applied to transform the stability analysis into a search for a static equilibrium state. Many properties related to the stability analysis are studied. According to these properties, we design an efficient algorithm for searching the static equilibrium state. The maximum allowable cutting force or the minimum normal stress, which are key concerns in automated design of fixtures, can be calculated precisely by using the search operation. The algorithm can also be extended to the case of multiply distributed friction forces with differently configured clamping areas. Several examples are provided to illustrate cutting force design for different fixture conditions.
Electronic cam motion generation with special reference to constrained velocity, acceleration, and jerk
(2004-07-01)
Liao, CS
;
Jeng, SL
;
Chieng, WH
;
機械工程學系
;
Department of Mechanical Engineering
Electronic cam motion involves velocity tracking control of the master motor and trajectory generation of the slave motor. Special concerns such as the limits of the velocity, acceleration, and jerk are beyond the considerations in the conventional electronic cam motion control. This study proposes the curve-fitting of a Lagrange polynomial to the cam profile, based on trajectory optimization by cubic B-spline interpolation. The proposed algorithms may yield a higher tracking precision than the conventional master-slaves control method does, providing an optimization problem is concerned. The optimization problem contains three dynamic constraints including velocity, acceleration, and jerk of the motor system. (C) 2004 ISA-The Instrumentation, Systems, and Automation Society.
Modeling and diagnosis of motion error of multi-axis machines using a ball bar test
(1996-09-01)
Jeng, SL
;
Chieng, WH
;
Lee, AC
;
交大名義發表
;
機械工程學系
The contouring accuracy of a multi-axis machine has a critical effect on the quality of many advanced technology products. One of the best approaches to assessing the contouring performance of machine tools is through double ball bar measurement. During circular interpolation motion, the machine traverses, with two axes at a time, a circular trajectory, with each axis subject to sinusoidal changes in acceleration, velocity, and position. The motion error is measured by detecting the relative distance between a point on the spindle nose and another point on the machine table and plotting this distance in polar coordinates. The present paper derives mathematical models and diagnosis procedures for first and second-order motion error resulting from the active degrees of freedom of a multi-axis machine. The theoretical results are verified by both computer simulation and double ball bar testing experiments.
Modeling of piezoelectric actuator for compensation and controller design
(2003-01-01)
Tzen, JJ
;
Jeng, SL
;
Chieng, WH
;
機械工程學系
;
Department of Mechanical Engineering
This work proposes a novel method for describing the hysteretic non-linearity of a piezoelectric actuator. The hysteresis behavior of piezoelectric actuators, including the minor loop trajectory and the residual displacement near zero input, are modeled by a set of hysteresis operators, including a gain and an input-dependent lag, as well as the parameter scheduling method. A hysteresis model, using the identified parameters, and containing only the dominant hysteresis operator, is presented herein. Based upon a simplified hysteresis model, tracking is-controlled to reduce the non-linear effects in the characteristics of the piezoelectric actuator. A proportional-integral (PI) controller, with inverse model feed-forward, suppresses the tracking error to within +/-1% full span range (FSR) of the actuator, noticeably improving the tracking performance of the piezoelectric actuator. (C) 2002 Elsevier Science Inc. All rights reserved.